Dynamo-electric machinery



F. CREEDY. DYNA'MO-ELECTRIC MACHINERY.

6 SHEETS-SHEET L.

Fig. l.

F. CREEDY.

DYNAMQ-ELECTRIC MACHINERY. APPLICATION FILED FEB. Il. I9l9.

Patented June 6, 1922.

s SHEETS-SHEET 2..

- r. CREEDY. DYNAMO-ELECTRIC MACHINERY.

APPLICATION FILED FEB. II. 1919.

Patented June 6,1922.

6 SHEETS-SHEET 3.

Fig. 10.

Internes F. CREEDY.

DYNAMo-ELECTmc MACHINERY.

APPLICATION FILED FEB-.11,1919.

1 Patented J une 6, 1922.`

6 SHEETS-SHEET 5,.

.3 I. I u

Ifjcnamr.` DY NAMOELECTRIC MACHINERY. APPLICATION FILED FEB. 11,1919.

1,418,779. 1 Pam-mun@ 6, 1922.

.6 SHEETS-SHEET 6.

lNvENToR nutrita sTATss PATENT OFFICE.

FREDERICKVCREEDY, OFILKLEY; EGLAND.

been fflesoribed in my former U. f5. .Patent lilo. l. .l .4i-24;.

lt is a ohie't' purpose ot this inyention to simigility the generating or supply apparatus 'Forsuf-a.iiiaehiuery by reducing thenuinber ot ph ases necessary to beiutulueed by suoli ap} iaralus. 'lo this end the invention Conteniplates the arrangement and interconnection of the `windings ot.' dynamo eleetrie machines iu such manner as in tact to produce phases intermediate betwist-xnj or ditlerent` trom. and additional to. the phases generated in the supply apparatus; and the invention further eonteniplates the design ot supply apparatus. such, as transformers. in sufi-h manner as to produce those particular phases only ot a polyphase supply Whieh are necessary tor the deriiation olE all the phases required by the partieular machinery to be.

supplied.

Alternatively. and in pursuance of theaboi'e objects the invention may be said to` be direeted to the interconnection oit sections ot the` Winding ot a polyphase dynamo eleo- 'irie nuiehine in such manner that the poly- ;jou or polygons ot lll. M. across such sections required lor the operation ot such maf-.hiue ou different pole iuu'nbers shall approximate as nearly as possible to the polyggon oi E. M. F. ot the supply.

ii'moi'e speeitio purpose of the invention is the production ot a Variable speed motor ou vvariable pole number, and iii particular ol a. motor capable of operating` on three or more different pole numbers, together 'with control apparatus :tor so interconnecting seetions oi a single Winding upon the primary member ot said motor as to produce Afor eaeh Specification of Letters Patent. Pateted-June 6, 1922, Application led February il, 3.919. Serial I\To.1226,263.l

polenumbera number of similar groups vof ampere conductors equally spaced upon said motor. and haring a common phase difference yproportional to the pole number. said connected groups `for constant E. M. F. across respeetive sections of the Winding and `siilistaniially. constant flux density in the airpanyingij drawings in Which- Fig. l is a, diagram explanatory ofthe analysis of a. polyphase supply ollai'ge numbei' of phases. i

F 2 illustrates a method ot producing such a polyphase supply 'from asupply of sin ll number of phases.

y. Fipzi shows how to transform a polyphase supply in phase transforming,` apparatus and in aniotor Windingto produce a high `number ot phases. y

4, and G illustrate another method .ot' obtaining an increased number of phases 'trema polyphase supply.

Figs. 7 and 8 show methods ot transforming polyphase4 supply to a different number ot phases with the same number of terminals.7 and how to utilizethe supply thus transformed n i F i g. 9 shows the simultaneous employment of the methods ot Figs. 7 and 8. f

Figs. l0 and 1l. are explanatory of ther I*ical rari-ying out of the method of Pip r'. y

Fig. is illustrative of the E. M. F. polyi, produced by a phase transforming apratus ando't the construction ot such apparatus. y l

Figs. i3 and la relate to the design of such phase transt'orining apparatus. Fig. is illustrative of the E. M. F. polyigons produced' by another phase transforming; apparatus and of the construction of such apparatus.

Fig; 1G is a diagram ot a phase transformingivapparatus and motor Winding explaining the various interconnections of the sec- Cfr tions of the motor Winding with each other and the phase transforming apparatus produced in the operation of the motor, control apparatus, and generating' apparatus shown in Fig. 17.

Figure 18 is a further illustration of the transiormation ot' a polyphase supply in phase transforming apparatus and in a motor Winding to produce a higher number of phases.

My former application above mentioned pointed out an advantage ot using for dynamo electric machinery oi'f the kind in question a number ot phases having no common factor with any ot the numbers of pairs of poles to be produced in the motor: the advantage being that with. this condition ttulirilled any given phase was never connected to more than one sect-ion of the motor Winding whatever the order oit connection between the motor tappinpgs and the supply phases. l3nt this choice oi phase number imports also certain limitations and requirements; the phase transformer must be capable ot transforming the Whole oi the power 'from the number ot phases oi" the prime supply to the number oit phases required by the motor; also each section ot' the motor being supplied by an independent phase. and the sections staror mesh-connected, the polygon of E. M. l?. across the sections ot the Winding was either a number oit equally spaced radii (for the star connection) or a regular polygon (tor the mesh connection).

lit the number o't phases chosen is not prime to the numbers ot pairs of poles these liniitatious and requirements do not hold. Certain only of the maximum number of phases required by the motor need to be produced 'in the phase transforming apparatus; and by interconnection ot the sections ot the motor winding the polygons ot' E. M. F. required by the motor may be considerably iuodilied in the direction oit approximation to the polygon olt supply.

Study olf apartieular example will help to uralte cle; r certain important notions in 'this connection. machine having 2G independent ser-tions or lgroups in its Winding will require 'l' phases when running; on one pole pair on any number ol pele pairs prime to the number o'f phases. l3nt when the machine is runnin@` on number ot pole pairs not primo to the number ol.l phases windingl will contain a phirality ot identical sub-divisions excited by the same irilizises. equal in niunl lo the `greatest common lactor ot the number ot pole pairs and the total.

number o'i' ltionsl For example it the machine is running on 9 pole pairs. the

greatest common factor is 9. and there will Vbe 9 sulz-diyisions each containing.` tour sections excited `by E. M, F. et relative phase displacement O degrees deinees. i8() degrees, and QY'O'degrees.

li this machine is to operate ou all num-- bers et pole pairs from i to 10. it will present the following` conditions i there must "u'mer capaiii'to embase. it ibase.. and

To supply this machine tl apparently be a phase trai ble ot converting the supply 6-phase. 9-phase7 i2-phase. Btl-phase. The )resent intenti lies this requirement.

The process oi" transforming; 'from the number ot phases olf the {supply to the large number required may be carried out iu several instead ot one4 it the large. nrunber is not prime.. Suppose a liqihase machine has to be supplied Vtrain a ifi-phase source; the 3G phases may' be ebnined iu two stages, ttor instance by (y transFormation from 3-phase to l2 phase, and from lQ-phase to 3G-plaisec or i''rfim Se to Q-ph se and iroiu 9 to 36, or again 'trom ifi te G-phase and iiroiii 6- to -pliase. .Fi l. shows 'for ei;- ample that a Bti-phase supply includes a group et phases. marked A. Yt'oriiied by tal-- ing every third phase. ot which ear-h disiriiaced trom its neighbors by 3f.) degrees. which 2groupt tciere'liore, constitutes a eeuu 'i plete lf2-phase system. ,ind the '-svluile 22u phases comprise and can be analysed into three such Qqihase sets. .'i. l. nach ser being; displaced trom neixlibor grees. So the first strfc otf trans t may be effected by a tri ner shown at P in Fie'. Q. thus tra" the i-phase supply into three l--ph tems diii'ering in phase by 'IH de; other Words this '.'irst phase trai distorts the E, M, polygon ai tue supply f .i Y )t T1 l" into a nine-sided polygon i. r Y L. rauu to `Whose \.erti;fef-i are al equal. and mais lld angles with one another ot' l() dea jreef-s dl degrees ttl() degrees. l() dejfrccf-i ll! degrees i lo() degrees. l() degrees fes HU degrees respectively. Tl gc oi" transforimition is clit hree other transformers S., S3. el irbi' transforms a B-phase system to izqihase. 12? These transformers may be assumed to be, it

the type indicated in Figi'. tl oi" uw 'l ing portions ot said primary Winding;` in

series with small secondary windings on other limbs ot the transformer. ln the case illustrated sinY ot' thephases are obtainable direct Afrom tappings on the -Lnimary winding, the position ot which is indicated in the ligure by the circles trisecting the sides ot the triangles primary windings and their l/l. l? s These three l-phase systems malte up the ilo-phases required.

There is no general advantage in thus attecting transformation in tivo stages instead of one; but iny many cases, the second stage. is suitably chosen, can be carried out simply by suitable interconnection ot the sections of the motor Winding; thereby rendering` the second set of transformers unnecessary; and in such cases the division ot the transformation into two stages materially simplifies and improves the phase transformer as compared with the transformer that would be necessary to effect the Whole transformation in one stage.

li 3 to 9, next to be described, illustrate different methods ot so effecting' phase-transformation in the motor Winding, applicable in different cases.

It tvvo sections of the motor Winding', for a particular number of pole pairs, require currents ot' opposite phase. both sections can be supplied trom a single phase of supply it' the connections of one section can be reversed. And generally, if the machine requires a supply ot an even number of phases, to a particular' pole number, the current in anyone `section ot the motor Winding Will. be opposite in phase to the current `in some other section. ln any such case,` therefore, the phase transformer need produce only one ot' every `pair ot opposite phases out ofthe total required, its terminals being thereby reduced by a halt; and each ot these phases Willbe used to supply tivo sections ot the motor Winding connected in series or in par-- allel and relatively reversed.

For example. Fig. 3 shows at P the diagram of a phase transformer supplied With three-phase current at .its terminals Lu L2, Lf., and givingcurrents of phases OO, and 300, i200, and 1509, 2400 and 2700, at its terminals c and o, c and (Z, c and The sections ot the Winding` Q of thebmotor, in this and in succeedingl `iipiues, are numbered consecutively in order around the circumference of the motor, their angular pitch in this case being PMO. They are connected as shown to each other and the phase transformer in relatively reversed pairs, and united into a star at The same method applied to the production of 18 phases in the motor, vvould involve a phase converter generating,` 9 phases, say in three sets ot three, so that the difterence in phase angle between the phases taken in order Would be 200, 200, 80", 200, 20", 800,

which represent the i 20", 200, 800; and mutually reversed sections in the motor Winding would produce the remaining 9 phases.

This method may be of value also in producing odd numbers ot phases; for instance by the application ot it in Figure i8 a converter C supplying; 9 phases spaced as above in combination 'with a motor 'Winding Mo banning,` relatively reversed sections produces all the phases oit an equally spaced 9 phas system. although the converter may notproduce those 9 phases itself directly. sind generally a supply ot any odd number of phases can be grot by the means which will produce a supplyot double the number ot phases. The advantage oi the method in such cases is not that it brings about any reduction in the number oit phases to be produced by the converter, but it enables the phases to be produced by the converter to be grouped in sets having a phase difference betweenthe members ot' eachset only one halt oit the phase required between the phases` required; the E. M. F; polygon ot the supply derived from the converter thus approximates much more closely to the E. M. l?. polj. Hon ot the supply to the converter. than would the E. M. F. polygon ot an ordinary supply of the required odd number of phases. Examples ot the application ot this method are referred to hereinafter in connection With Figures l2 and l5.

Intermediate phases, additional. to those ot the supply, can also be obtained by joining the sections olf the motor :in combinations ot star and mesh connections; each junction pointbeing common to three sections, tivo, say, forming part of a mesh, and the third forming part of `a star. For instance the junctions oit a set of mesh connected sections may be the mid-points of the limbs of another mesh, ot' which each limb comprises two sections. A `typical example ot this method is shown in Fig. Ll, in which la section forming one ray of a star is connected to every junction of two sections forming; limbs ot. a mesh, the mesh, in other Words, constitutingthe centre of the star. The case illustrated is the production of 8 phases, differing by d50 'from a Ll-phase source joined to the terminals L1, L2, L3, L4.

Vlll/rese tivo methods ot obtaining additional phases, or in other words oit modifyinn` the polygon of iid. hit. F.s required by 'the motor, may be con'ibined. An example ot their joint use appears in l? Where a B-phase supply to terminals L1, L2, L3, produces in effect lQ-phase currents in the motor Winding, the s-ctions of which are joined in relatively reversed pairs to 'form the rays and limbs oi a three ray star with a 'triangular inesh inits centre. As before explained the numbers shoiv the order of connection ot .the sections, Which are supposed to be numbered in consecutive order i, n'ferenee ol3 the mozor. ll; .er ibut l@he relatively reversed l un ille slur rays joined in pure-.lle

eon'ibinuti ,n has a eren ol" erininzils. :is 1u The Ll--phzise ei;- ifive wmsuilffued above lhe number on? 1 :Hulot be 'further doubled by Inueuul 2O reversa. ol seeeions. Thus rho mesh-stur connection combined with reversal olf seetious will not produce lG-phuse from 45.-- ohsse. lhougrh they will produce QO-phuse 'from :"wohuse or -phase il'rorn T-phuse, or SG-phase 'lroin Q-phsse. As un example 'lhe lzisl;` o lf these uses ,is illustreed by e skeleton rlizxorun'i in Figi. 6^ in which euch line ieiln'esens u 'per olf sections reversed, 'those iu the stur rays being' preferably in parallel :uid lihose 'in the :nosh linibs in series as in Fig.

third method of phase trunsforniotion which een be carried out by intereonneeaing)- soolions of ihe inoo f winding; is the inethod of ohzrnging u supply oi one number oil? phases to another niiin'iber of phases having the seine numlier or terminals but u dill'erent E. lfl` l?. polygon. The most eoinmon zunples of 1his nre the change ,from S-phuse to Q-lihuse sind the converse. This by the use olf mutually reversed coils gives :S-phuse lo Ll-phzise. ll; may be carried out by the rl-coil" method olf trims'forumtion-T-oonneo- 'lilou-or by the QI-phzise zl-wire method-he L-oonneetion-botl or which methors in- 'volvo il terminals insiead or four. lt is essentiel hut all sections of the motor Winding should here the saine number of Jurns und therefore exactly the saine Voltage across them. el Coils joined as two T-oonnested pairs or i'nutuelly reversed coils, require therefore un lll. l/l. l?. polygon in the shape olf un isoseeles triangle olf which the height is equal to the bese. The phase truns'iruier hos to disort to this shape the eouilulerul triangle which constitutes the lil.

. l. ll". polygon olf un ordinary rl-fphuse supply. This is shown in Fig. 7, ln. L2, L,

,i M. l" polygon olf subply, D, E, F, Y Jl. F. polygon required by the motor; the lines joiuii l), E, l?, to Ll, L2, L,y respectively represent the secondary windings required ro effect the distortion. The ligure shows also how the sections of the molgor windino :ire ioinml 11o lho Transferium* :url in s rr ll.

the l'our senr-ions are L-eonueoted in all): reversed rulli-s. the l. lill. l?. polyhey Ternure is un isosemes irisngle of whim rho heiggh is lio/lf the bese. The neoesmy distortion is elleelod us indieuted in Fig. 8. where tru former converts from -l-phuse :it J:terminals L lug. lo 4l loliuse For ifominrolfiou :it lx-iruiiiluls G., lil. .l-` which are `ioined i'o 4lzhe motor sections und lhose lo e-ifxh other :is shown.

' T-oonneelgediund the reinsimler L-ooini n'iuruzil reve-iwal olj serious l:ieiif1'l'o"iunlilou ello-lod lio fil-obese fis sl 'wu in lio'.

es olf rho riufuie o' A -eounered soeliious fuirulrlrel, l l sgoom'u'lepv' i'viu'liu/rs connected llo ihe simio 'ieriuiuuls o supply. lli rhe l. l. riui I Y, @u us repi i r les z, runes-3s erich "iY i ious. ine r u ful. triangle foi i sections to lio bose or' 'the nr ighe lfeoir nestor sections is und the ratio l the heights ol" the Wrangler` 2 to \/Z.

ourlisiivrilizi o triangle Lv lig. li

ne lxs or Suid. triii le Pulls ol' llxeir buses e :ulizu'eul' sides ol lho ilouoguiiihls o lE Jhose sides. ro eorresnond n" 1 Figs,

.he secondary Win l- But :i 'l`eonuL-Ci'ion e orily employed in un ,ii any niuehine iu which l ings To ro prmli. e u um c'erlain wond' "i l'he moquer-,lions :"hou'ii lul ue curro; ui :anello :1: 2 imi l 'l0 in whim-h 1 current in seelions l und @il l )fr is .he

Current in section lie reni or und opposite 4l. These oui-rents iro such sum olI illund UG is equal to Oft (as in a balanced 37phase system), and the vector difference OC-OB is equal to 20A and. in quadrature with OA. f

Now if the sections l. 2. and 1i of Fig. i' form portions of a two-layer vdrum winding` having. say, three slots vper section. with the conductors connected as shown vin Fig. l1. the three slots of section l haveboth their inner and outer co'orhic'ters earrying` a current A of phase @A Fig. l0). so `that the total` current. per slot is 2A and in 'the three slots of section 3 the total current is -nrr: while in the slots rof section EZ the outer conductors carryv current B and the inner conductors carry current "C, making the current per slot B-C; and similarly the current per slot of section is CEB.

lt follows then lthat if such a winding` be supplied from a. triangle of E. M. F. such as indicated in Fig. '7, the total current in the slots of section el will be twice the total current `of the slots section 3, say` and in quaf'lrature with it; and the current 4in the slots of section 2 will be equal and opposite to the current in the slot-s of sect-ion 4.. Hence, although the sections of the winding do not carry Q-phase currents, the dis.- tribution of E. yM. F. is identical with that in a 2-phase motor.

The satisfactory employment of the T- connection is not however limited towindings in which the phases B and C, i.. e. the sections of the two short or horizontal arms of the T completely overlap; it is generally su'liicient if there is some overlap. Vilhether in any particular case the magnetic field will be too much distorted can be ascertained by constructing a diagram a ccording to .l'lelliminds method, (see the Transactions of the American Institute of Electrical Engineers .1.908 vwi th Graphical Treatment of the lotz'iting Field).

.The practical application of these various methods of ph ase transformation in the production of a machine of variabley pole number will be made clear by considering their employment lupon a machine `such as has heen referred to having 36 sections and requiringa maximum of 36 phases.

.lt has been shown for instance that 3- phase may be transformed Vto l2-phase by the motor winding, which for this purpose .1t have l2 or a multiple of l2 sections lf this formation a phase transformer is required oil' the kind shown at P in F ig. 2, which conrerts the 3phase supply into three 3-phase siqipliesdisplaced .l-O degrees one from another. Phase transformers such as S, are not needed, butinstead thesections of the nwtor winding to which the phase transformerl? is joined are interconnected in the mannershown in Fig. 5, so that each of the -.phase suppl fromthe transformer .gives 'at l0 degrees from each are parallel..

be made the final stage of trans-v rise to l2fphase E.` M. `Fis in the motor windings. To supply the 36 phases by this method then, necessitates only a trans- Afqrmer having 9 terminals arranged in 3 sets o' 3.

Another method of interconnection for `producing 36 phases has4 been explained with reference to Fig. 6. If this be adopted the transformer again needs but 9 terminals, but in this case the phases to be supplied from the transformer are equally displaced other; hence the shape of the E. M. F. polygon required by `the motor is not so similar as in the case just described to the E. M. F. polygonof supply.

It has been shown above that if this motor with 36 sections in its winding is to work on all pole numbers from 2 to 20 it requires y other numbers of phases besides 36, namely 4,6, r9, l2 and 18. It has been shown how 6- and lQ-phase can be obtained direct from the 3-phase supply by suitable intereonnection ofthe sections of the winding. lt has been shown also how 9-pl1ase and IS-phase may `be obtained by the use of a transformer which distorts the E. M. F. triangle of supply linto a 9 sided polygon the radii to whose vertices are all equal andv spaced apart by angles of 200, 200, 800, 200, 200, 80o, 20o 200, 800, respectively. The i-phase can be produced by either the T or L method.

Fig. l2 shows the diagram of a single transformer for giving all these necessary numbers of phases. The dotted triangle L1, L2, L3, is the E. M. F. polygon of the 3- phase supply; the polygon B1, B2, BQ is that for the three Sets of 3-phase with l0c displacement between the sets for giving 36 phases in windings connected as in Fig.` 5; the `polygon DEF is that for li-phase with T-connection; the polygon K1, K2, K3, lif'is that for 9 phases displaced 20", 80o, 20C. successively as stated above. The second ary windings shown by wavy lines from the points LM L2, L3, are wound on that limb of the transformer which carries the prim ary winding (XL1, ete), to which they Some phases `can be obtained by tappings without secondary windings, viz. 13 K1, BMIQ, B7 and KT. Phase D is obtained by la short secondary on the same limb as the primary to which it is connected.. Phases B2, K2, K3, B3, E. B5, K5, KG, B6, F, BNKS, Km and B.) are allobtained from six comparatively short secondary windings on the limbs of the primary phases to .which they are parallel. Thus all the phases required are obtained with comparatively little transformation from the 3 primary phases.

ln some cases, a reduction of the number of Ysections :in the motor winding materially .lessens the number of phases required to 'produce a particular nuuiber ol poles. For instancenl in a Winding' with 5)(3 sections 'l2 phases are needed to produce (i poles; iifhere as it the winding' had but t8 seetions 6 phases would ijiroduee 6 poles ln these eireumstanees it may be eonrenient to reduee the number ot sections of the W'nicling` on particular pole numbers, whichv may be done either by joining' pairs of sections in Series. and treating' theni as single sections. or by leaving certain sections idle. The particular method o'll Connection Where seetions are joined together depenffls on the partieular purpose in vien@ but in `eeue'ral there must always be the saine total number ol turns in each phase. The oase linst n'ieiu'ioned is met, by `joiniin;` adjacent; pairs ot sections in se ries. ln another misen lor instance7 it flo sections hare to be redueed to 24- so that- S poles may be i'nodueed bj. 6 instead of' 9 phases. ever).Y third section may be lett intact. and the pairs oi sections betr-reen joined ,in series. To suit a Als-phase suppl?,v there ma)Y be tiro ser-tions joined ,in series. YtolV- lowed bv tiro more sections joined in seriesA liollowed by tufo single set-tions and so torth. .nd occasionally it may be vtound an ad if'antage to use alternately tiro and three sections connected in seriesn of tiro and tour., or three and 'tour and` so on. fn oeneral. the total number ol resultant oileetwe seetions, Whether single ones or ofnnposed ol" tivo or more adjacent seetions 'in series,y Will be proportional to the pole number. more seetions being Combined in series fie the pola number `required. is redueed. Fluch intern Connecting' oit the sections may. ot Course. be done by the Controller. and need not atleet the motor itself.

llY the sections are lett idle they should be uniitorinlv spaced armind the pi-rril'ilieifi7 o the Winding; tl method is onli7 possible When the nun'ibor ot sections lett idle if; equal to or a multiple olz the uiunber oll poles. ..f`\.n example is the reduction ot llseetions to ld, in order that G instead o'l P phasee maj-f suire to produce 6 poles. bj: lefrvinoj every: fourth seetion idle. l

The seleetiou ol' the moet suitable methods oli iuterffuuieetiou lli-oni among' those above desfril'ied. Vlor a partieular niaehine required to operate on partieular pole ninnbers is bes?-` nlade by studying; he rotating" field by Hellinunds method already rei'ierred to. the nue ot Whieh in the desi4 n ol Inafhines ol this clase has been def-sffribed in my YFormer ap plieation.

To obtain the greatest possilfile output from a u'iotor the speed olf i ieh vis varied br Changing' its pole nuudiur, C l

'tue du?? densitif in the air Qiap nlnet be kopt anproximatx Constant all pole nuinl'iors. This#` i.= i'olres eaeh ser'tioii of the n'iotor Winding?? haring; applied, to it a rol-ta approniniajely 'tor proportional to the speed ot the inaehlne; or: to he more enact. taking account oi the "rf "iation ol pitch. approirimateljv WODOV tional to the speed ot the motor multiplied by the ehord 'breton Whieh is the sine ot hal l" the angular pitch This decrease in the ser our" f volta applied to the motor mayi be obtained by inerea ing' the primary turns in the phase ronrerter bj the o'll tappingf-S. or by other methods alread-l reterrod to. vVariation ot the priu'iarj" turns @banlieu the magnitude all 'the secondary roltagjes without eliangine their phase relation. Bi means ot the various methods :'leseribed it is possible to riet almost ani.r voltage desired across any seetion ot the rifindinp; at any speed Usually one ot the possible connor tions described will be -found to `Q'ire ap proxiniateljf the required if'oltage. But iii" resort is had to .f'ariation ot the primalv turns ot the phase Converter. suol variation should be lrept as small as possible ir. order that the ."ffni'erter itf-elll ina.;7 be lient small. {lonsequently it is a Consideration to be. borne in mind in des'gu to so spleet the methods o1? eonneotion that the lon'er the siieed the more sections tliei are in series; and similarly mesh Connections are ratliei` to be preferred 'for the high speeds and star conuertionsv Cor the loir Speeds. J\.,n instai'lee o'" .Guelfi selection is to be seen in the fl-pole connection ol' Fig. lll hereinafter described. d nd anolher vmalivv be tout d in the motor with il?. seetions alreadjr Considered. That motor l'or either 'poles or l@ poles required il pbase lil. lll lilfs. eonsistiue ot three l--ilihasfi eets displaffed Q0 degrees from each other. lt is then nonrenient to have two aeetions in series For .oaoh phase :For the q pole bonnen lioin and "l se''iona in seri-esi *"or the lf3 pole f'onuertion. (lr a rather less exact approviniation to the desired oonditions nia).Y be lgrot b r uylug' the Afl: sections iu series mesh-oonnerted tor the nel@ Connection. and l ree- :gions in seri star-connected tor the 1G pole eonneetioiu rllhe (lesen ot a phase transformer o 'I' the type desfiibecl with refeii'enre to 2 or YFig'. l2 facilitated by the oenstruetion oF a refftor diagram tor it in the manner shown in Fig. 13. Veetors Nl, N. O. at l2() deulees with each other represent the primari.' ll. M. ls. (lireumseribe a heiragron about these vectors. so tl at from the end of' each rector entend tiro sides ot the hexagon pan allel to the remaining renters. lnteroept1-; on lil/rese sides will then represe it E. M, Ffs which can be obtained by secondary WindV4 inge on the limbs ot the transformer to Wliioh the sides are parallel. Any eirele l?. .intermediate in sir/,e between the insoribed and eireurnseribed eireles will eut the sides oi the hexag'on symmetrieall ifY on either si de of each vector, at M1. M3. N1, Ng, OH O3,

. vector dia and will also out' the vectors themselves as at lift?, N2, O2. it radii be drawn tothe pointsI M1, M3, etc.7 those rad-ii represent E. M. .F.swhich can be got vby join-ing in series with the primary winding represented by vector M, for instance.v a secondary windi ing represented by mit.whicliis on the limb carrying the primary winding represented byN and has a number of turns represented by the length M M3. Similarly the inten cepts am, no. an, om7 mo represent secondary windings intended to bcjoined to the primary winding indicated by their` iirst letter and actually Wound on the limb indicated by their second. letter. Further the intersections M2, N2y 02 represent taopings on the respective primary .windings By suitable choice of the size oi? the circle the angle MXMS can be made to have any value desired, for instance, l() degrees or 2O degrecs, to produce the transformer tor supplyingl) phases l'or conversion into '36- phase. or one supplying 9 phases for conversion into 18 or` into av regular .fl-phase system as above described.

The method. is et general application. Il?y live or more sets oi B-phase vectors are required they can be got by drawing a second, and il necessary a third and fourth heragon p from tapping points in the primaryl vectors so placed that the intercepts cut oil1 by the circle R give the desired valuesi'or the angles llLXM, MXM'r, etc.` it an even num bei' of sets ot phasesis needed the intersection ot the circle with the vector itself is disregarded. y

In an alternative method of drawing these o"ainsi the iirst `lieizagonmaybe drawn with three of its sides 'at right aiigles to the three vectors ot primary E. M. F.

ln this case the outer end oit each oii these vectors lies at the inidepoint'ot one side oit the hexagou instead of at oneri i its vertices;

A simila r method ot design applie-iv il" the supply is other than `Sphase. For a Qspliase lf-wire suiiply oney or morersquares will re- )lace the hexagon or hexaffons and in this c t: 'l

case also the ends oit the star-connected winch ing may' preferably lient the mid-point of the sides of the square. y

Atranstoimer ot similar type can be used to supply' motor sections whichvare Tlconnected or il.connected.iorftheA production of 2- or l-phase- Its designby the aid of the vectordiagram will be understoodflirom Fig.y

3 fin isosceles triangle such as DEF, the height. of which is equal to itsbase,` is Vfirst drawn. il. regular hexagon isthen superposedon this' so that the verte-x oil: the triangle lies upon a radius ot thehexagon or upon its irolono'ations.` while the ends or the base lie on the opposite adjacent sides of the lieiiagon or on their prolongntions.v Threeradn XL1g XL-7 XL3 ot this hexagon `represent the star-eonnected frlfphase pritransformer previously described for disA torting the equilateral triangle of E. M. F. to an yisosceles triangle whose height is halt its base may conversely be employed to produce an equilateral triangle oit E. M. `F. from the 2-phase supply; by which means all the connections oi motor windings and phase transformers already described are made'available with Q-phase B-Wire system.

Fig. l5 shows the E'. M. F. polygon oli a phase converter receiving l-phase current and supplying phases up to 24. The triangle L1, L2j L3, represents the E. M. F. polygon ot the B-phase supply. The triangle is the polygon tor et-phase with T-connected windings. The polygon T., T2, TG', is that for producing i241 phases b v the aid ot two sets ot lmotor windings counected to transform B-phase to lQ-phase; the angle between the radii through 'l1' and Tl is lo. that between T1. and T2 is i050 and-so ou. The polygonlll. U2 UG is similar tofl., T2. T5 but gives reduced voltages 'for use on lower speeds. It is to be noted that the horse power output of the motor is reduced as the `speed decreases: lien/fe "tor low speeds the transformer is more lightly loaded and thereiore it is per` trollcrld'Y ior intercoiniecting said sections among themselves and to the terminals of the phase transformer. For the sake ot clearness the trai'isi'oi'mer is shownas having a separate primary winding Y provided' with tappings by vwhich the number o .F turns in the winding can be fariedi but naturally1 the supply may be'joined to the saine wind` ing as is connected to the motor. and the only secondary windings necessarily required are the small sections-such as LIF the construction and function oiiwhich has been already explained.

11.: is immaterial to the present invention what tipey ot control1e1 1V is einploved. Suitahle -consti-urtion 11'1 controller have been indicated in 111;" 1"'11111111 specification particult-r11Y 111th reference to 11113'. and Fig'. thei'cot.

1n apply] ej such controllers to ther motors 1112 the present :11j/*111icationn the sections ot the motor ivindinr need to 11e ioined hoth to hns-bars and to lnfiislies.` and it is 111" advantage to yioin the phases oc to 1111s- 11: sA ,lt is not alwajs nec-` 1111iY the ends of over);Y section to terminals. .11i the total 111111111111' o'l'i sections is even7 the oppositeA sections will 11e in opposite phases on odd numbers ot pole pairs. and the same phase on even pole pair numhen. n1 av thcretore 11e possible oin two ends o1 such sections toejetl'ier :11111 bring); out the junction to a sine'le terminal; supplvinn the sections in parallel tln'ono'b this terminai on 111111 numbers ot pairs et poles. and sup-A pllvingY them in series Without Using the junction terminal 1111 even numbers ot polo pairs: or vice versa it the sections are so joined as to he mutnallv reversed.

The motor chosen 'lor ill nstration in Fi 1G and 17 has F241 sections which are nnmbered eonsecutivelv and occnpv on the motor the position indicated in Figi', 17; it is 1111 erated trom the 3-phase prime sonrce Z: and the phase converter is designed to snp- 1111,Y all the phases necessarv tor the operation ot the motor on 4-` on U1 1Q. 14.- and 1G poles: the phases not supplied bv the con verter hein;vr produced in the motor Windi111; 11- 11 interconnection ot its sections in the manner aheadv descrihed and shown in 11etail 'For cach case in Fig. l@

For 1-p11le Working' the current is taken direct from the fi-11hase supplv. The sec-- tions are ioined as star 111111111111 nach rav is made 1111 ot tour parallel sets oi 1111711 se@ tions eacln halt' the sections being reversed.

The Q-pole connection is the same in toi-111 as that tor 4-1111les. hut the sections are joined in a different order,

For 11i-pole Worlrinir use is made o1 11111 combined star-mesh connection. The sections o1 the Winding are divided into two sets` each of which forms a. R-limh mesh in the centre ot the 9--rav star. each 1iml1 consisting` 111 two mntnallv reversed sections in` series and eaco iav ot two mnt-11111117 111V versed sections in parallel. Flach 111 these sets converts 3-1111ase to 12phase. and as: the one set is supplied 'From terminals T11 Tf1. T77 and the other trom tei-11111111111 rl`. Tp. T" i. e. trom two pl1ase snpplies dilterinnj in phase trom .nach other hv 15 1111- arees the 1111111111 111111111 is to produce .94- phases in the 1111111111111.

The 12-po1e connection is an example o1 the application of the Tconnection. rDRF terminals UU U2,

are converte-r terminals which give a 41- phase supply suit-able 'tor T-conneeted Win11- ings. The odd numbered sections in tivo mutually reversed parallel lgroups ot (1 sections in series form the vertical limb o1" the T each of the horizontal limbs consist-- ing' of two parallel groups ot sections in series.

The ls-pole connection is again. the nime in `form as the lO-pole connectionr hut 1v1 th a differentorder ot connection ot the sections, and as the speed With this connection will be lower the terminals are joined to 11G instead o1" to the terminals T1, T2 Tn of the phase converter' so reducing' the voltage per section.

For l6-pole Working` the snpplv is :11111111 'taken direct from the B-phase terminals L11 L2, L5; the sections forming1 a 3-11111 stan each row of which consists ot 2 parallel groups ot L sections in series.

Consideration ot these examples ot eonnection reveals various simple rules govern* ing the phase relation ot the sections tor di '1"- terent pole numbers, a knowledge of which helps in the design ot the connections. For example it the total number ot sections is even, so that each has another diametricallv opposite to it7 any two opposite sections will be in phase on even nnrnbers ot pole pairs, and in opposite phases on odd numbers. Also any 3 sections differing in position bv one third ot the circum'terenee will be in phase it the number o? pole pairs is 3 or a multiple ot 3, and otherwise will 'Form a regnlar S-phase system. Similarly 4t sec. tions uniformly spaced around the circn1nterence Will` form a regular -phase svstem unless the number ot pole pairs is divisible 11 v 41. in which case the sections are in phase` or is divisihle bv 2 and not bv f1 when opposite sections are in phase and intermediate ones are in opposition of phase.

Stated generallv the rnle is this, that n coils nni'tormlv distributed aronnd the circnmterence ot the Winding' 'form a regular s vstem o t 79-phases except when the number ot pairs oil? poles on which the machine is running1 is a multiple of p when the coils are all in phase7 or a submnltiple of 71,

in which case the coils 'form a s vstem or systems of w phases.

In large machines the change trom one speed to another may cause considerable momentary rushes ot current. which it is desirable to avoid or limit as 'Far as possible. For this purpose it is preferable to otter-t a change of speed in two steps. First the pole number is changed sav 'from 71 to ,1 -2, and simultaneously the machine is switched on to a voltage less than the normal bv means ot' resistances or buv the use oit tappines such as are shown on the Winding Y in Fig. 17,

or such as U1, U2 U6; then by a second movement of the controller the voltage is restored to normal value. The reduction of voltage is required both in increasing and in decreasing speed.

It willbe understood that the particular windings described are examples only, and should not suggest that there is any restriction whatever upon the number or sections a winding can have. And the windings described, though chieflyy considered as windings of a motor, may be the windings ot any machine requiring various pole numbers to be induced in it.

lVhat I claim is zl. In combination, a source of a system ol balanced polyphase E. M. F.s oit small phase number, means for deriving therefrom a plurality of systems of balanced polyphase E. M. F.s of the same phase number constituting together a system of larger phase number with unequally spaced phases, a dynamo electric machine, a primary winding on said machine divided into sections, `means ior interconnecting those sections and connecting them to the said f system of unequally spaced phases so as to produce in said sections a polyphase system of currents with a constant phase difference between neighbouring sectionsoi yet larger phase number 'forming a given number of poles, and means for 'connecting said sections together and to the supply so as to form a different number of poles.

2. In combination, a source of a system of balanced'polyphase E. M. F.s,-means for producing therefrom a number of systems of balanced polyphase E. M. F.s differing from each other by a phase angle less than the angle between thepha'ses of one system divided by the number of systems, a dynamo electric machine, a primary winding on said machine divided into sections,` means ior interconnecting those sections and connect-` ing them to the said systems of polyphase E. M. FFS so as to produce in saidy sections a polyphase system of 'currents with a constant phase difference between neighbouring sections forming a given number of poles, and means ifor connecting said sections together and to vthe supply so to iorm a diilerent number of poles.

3. In combination, a. source of a system of balanced polyphase E. M. F.sa dynamo electric machine, a primary winding on said machine divided into sections, means for deriving from said source a number of systems of balanced polyphase E. M. F.s difiering from each other by the phase difference required betwen adjacent sections of said winding for a particular pole number, means for joining said sections in mutually reversed pairs, means 'for interconnecting said reversed pairs with each other and with said systems to produce said pole number so that the same number of `sections is supplied iirom each of said systems `and of the sections supplied trom any one system half` are in star and halt in mesh, and means 'tor dilierently connecting said sections to each other and the supply so as to produce a diti'crent pole inunber. Y j y 4, In combination, a source of a system of balanced polyphaselil. M. F.s, means for deriving therefrom a system of polyphase E. M. Ffs of higher phase number with Vunequally spaced phases but having an E. j M. F. polygon approximating to that of theoriginal system, a dynamo electric machine, a primary winding on said maol'iine divided into sections, means ior connecting said sections to each other and the system with unequally spaced phases so as to produce in said winding a system of polyphase currents witha constant phase diiilerence between neighbouring sections and a particular pole number, and means ior Aconnecting said sections together `and to the supply so as to produce a different pole number.

5. In combination, a source of polyphase supply, a dynamo electric machine, aJ primary winding on said machine divided into sections, .means for joining neighbouring sections in series in sets symmetrically spaced around the circumference so as to iorm composite sections andlor joining the sections together and to the supply phases to produce a particular `pole number, and means for disconnecting the sections `of a set from each other and joiningthem to different phases of supply to produce another pole number. j

6. In combination, a polyphase supply, a dynamo electric machine, a primary winding on said machine divided into sections, means i'or joining said sections in order to the phases oi supply to produce a particular pole number, means for joining some or said sections in sets in seriesto form composite sections evenly spaced around the circumierence, and means for joining the remaining sectionsand said composite sections to veach other and the supply phases to produce another pole number` 7. In combination, a source of polyphase supply of phase and voltage suitable for T and L connected windings, a dynamo electric machine, a primary winding on said machine divided into sections, means for joining some of said sections in T and others in L, and means for connecting said groups of sections andjoiningthem to appropriate phases and voltages of supply. i y 8. In combination, a source oi polyphase supply, a dynamo electric machine, a primary winding on saidmachine divided into sections, means for joining said sections to the phases ot supply. in different orders vto produce diiierent pole numbers, and means for joining sets ot neighbouring sections in series symmetrically throughout the winding, and for connecting the sections thus compounded to the phases ot supply so as to produce another pole number.

9. In combination, a polyphase source otelectric supply, a dynamo electric machine, a primary Winding on said machine divided into a number or sections, means tor connecting said sections in a plurality of di tferent relative arrangements to the source of supply so that E. M. F. polygons having,- a number of sides greater than that of supply but less than the number oit distinct phases of current in all the sections applied across said interconnected sections produce 'for all connections the same number of bands ol' current equally spaced in pl e relation, but for each connection a ditlterent phase displacement between neighbouring sections, and means for distorting the E. M. l?. polygon ot supply to the 'forms required for said different connections.

l0. In combination, a polyphase souri-e o'l electric supply, a dynamo electric machine, a primary winding on said machine divided into a number of sections, means for interconnecting` said sections in mutually reversed pairs in a plurality ol different .vays so that E. M. F. polygons having` a number ot sides greater than that ott supply but less than the number oil3 distinct phases olf current in all sections applied across said inten connected sections produce 'for all connections the same number of bands oi current equally spaced in phase relation, but iter each connection a different phase displacement between neigl'ibouring sections, and means tor distorting the E. M. F. pol;v of supply to the terms required 'lor different connections.

1l. In combination, a polyphase source ot electric supply, a dynamo electric machine. a primary Winding,` on said machine divided into a number oit sections, means tor interconnecting said sections halt in mesh and half in star relation in a plurality oi dill'ern ent Ways so that E. M. F. polygons haringa number of sides greater than that oil supply but less than the number olf sections applied across said interconnected sections produce 'for all connections the same number of bands of current equally spaced in phase relation, but tor each connection a diiierent phase displacement between neighbouring sections, and means for distorting the Il. M. F. polygon of supply to the 'forms required for said di'li'erent connections 12. In combination, a polyphase supply, an electric motor, a primary Windimg on said motor divided into sections, means tor joining said sections in T to each other and the supply to produce a given pole number, and means for joining said sections into a mesh in the centre ol a star and `lor joining the terminals olf the star to the supply to pio duce a different pole number.

In combination., a polyphase supply, an electric motor, a primary winding` on said motor divided into sections, means Ytor joining said sections in groups in series to each other and said supply so as to produce a particular pole number and a particular number of zones of current around the motor circumference and means i'or join'ins;Y said sections in groups in parallel to each other and said supply so as to produce the same number ot Zones oi' current to a smaller number et pole pairs.

lt. In combination, a polyphase source et electric supply, a dynamo electric machine, a primary Winding` on said machine divided into a number or sections, means :tor inta connecting,` said sections in mutually reversed pairs to form a mesh. in the centre ot a star in a plurality ot di'i'erent ways so that E. M. F. polygons havingl a numl r ot sides greater than that ot supply but ly than the number ot sections,l applied acr( said interconnected sections produce Ator al connections the same numl ir oit bands o current equally spaced in phase relation, but for each connection a diilierent phase displacement between neighbouring' section:-;, and means for distortinm the E. lla. l?. polygon ot supply to vthe terms required for said different connections.

l5. In combination, a polyphase source oit electric supply, a dynamo electric machine, a primary Winding on said machine divided into a number oit sections, means ttor interconmafting,` said sections in at least three dit- Vferent ways, so that E. M. l?. polygons approximating to that ot supply applied across said interconnected sections produce at least three di'l'lerent numbers et poles but substan-` tially the same l'luf; density in the air gap, and means for distorting the Ill. M. l?. poly-- gon oi' supply to the lforms required Vlor said dil'llerent interconnections.

i6. In combination, a polyphase source oit electric supply, a dynamo electric nia chine, a prin'lary winding" on said machine divided into a number o'lf sections, means tor intern connecting said sections in at least hren dill terent Ways so that ll. M. ll1 polygons approximating to that of supply applied across said interconnected sections produce for all connections the same number of bands oit current equally spaced in phase relatioinbut for each connection a di'l'l'erent phase displacement betvfeen neighbouring sections, and means for distorting the Ill. M. F. polygon of supply to the 'forms required for said different connections.

17. In combination, a polyphase supply, an electric motor, a primary Winding on said motor ol the twodayer drum type divided into sections, and connections between said sections and the supply joining them in.T, the sections belonging to the two parts o the bisected phase overlapping upon the pe riphery ot the motor.

18. ln combination, a dynamo electric machine, a primary winding on said machine divided into sections, a source of polyphase supply, and means for interconnecting said sections with each other and the supply so as to form parallel groups and mesh connections producing low pole numbers, and so as to form series groups and star connections producing high pole numbers.

19. In combination, a polyphase supply, an electric motor, a primary winding on said motor divided into sections, means for connecting said sections in star to each other and the supply so as to produce a particular pole number with a particular number of sections in series across each phase of the supply, and means for connecting said sections together and to the supply ina dit ferent star, havingv more sections in series across each phase and producing alarger pole number.

20. In combination, a polyphase source of supply, an electric motor, a primary winding on said motor divided into sections, means for joining said sections to each other and the supply in star, so as to produce a particular pole number `with a particular number of sections between two terminals of the supply, and means for joining said sections to each other and thesupply, so yas to Jform a mesh in the centre ot a star vand to produce a larger pole numberwith a larger number kof sections between any two terminals of the supply. j

2l. A method of producing a given pole number in dynamo electric machines which consists in selecting symmetrical groups of sections which require the least phase difference between them for that pole number for connection to supply phases, and joining `to each section of a group all other sections which require the same phase as'or kthe opy posite phase to that section, and finally completing' a connection between a section of one group and the corresponding section ot' another group through sections which require a phase mid-way between the phases of said sections, or a phase in opposition to such mid-way phase. j Y

22. ln combination, a dynamo electric machine, a primary winding on said machine divided into sections, permanent connections between opposite sections, and a controller joined to said permanent connections and to the remaining ends of said sections for connecting said sections together. and to the supply to produce different pole numbers but always thesame number of Zones ot current. l

23. In combination, a source oi a system ot balanced polyphase E. M. F.s, a dynamo electric machine, a primary winding on `said machine divided into sections, means `lor deriving `from `said source a number ci' systems oi balanced polyphase E. M. Ffs dirl'ering from each other by the phase diiierence required between adjacent ysections of said winding for a particular pole number, means :tor interconnecting said sections with each other and with said systems to producesaid pole number so that the same number oi' sections is supplied from each of said systems, and or' the sections supplied v.trom any one system halt are in star and half in mesh, and means for differently connecting said sections to `each other and the supply so as to produce a different pole number. b

24. in combinationa source ot a system of balanced polyphase E. M. F.s, means for deriving therefrom a number of systems of balanced polyphase E. M. Fis constituting together a system of larger phase number with` unequally spaced phases, a dynamo electric ma`chine,.a primary winding on said machine divided into sections, means for joining one half of said sections in mesh relation and the remainder in star connection each star ray being joined on the one hand to the angle 'et a' mesh and on the other 'hand to a phase oif said system oli larger phase number so' as to produce a particular pole number, and means for oin-`y ing said'sections toV each other and the supply in a different relation to produce another pole number.

25. In combination, a polyphase source of electric supply, a dynamo electric machine, a primary winding on said machine divided into a number ofsections, means for interconnecting said sections half in mesh relation and the remainder in star `arms each radiating from a mesh angle in a plurality ot different ways so that E. M. F. polygons having a number of sides greater than that oi supply but less than the number otsections applied to the ends oi? said star arms produce for all connections the same number of bands oit current equally spaced in phase relation, but it'or each connection a different phasey displacement between neighbouring sections, and means for distorting the E. M. Fy polygon of supply to the `forms required for said diiierent connections.

26. In combination, a polyphase source of electric supply, a dynamo electric machine, a primary winding on said machine divided into a number ot sections, means for interconnecting said sections in mutually reversed pairs half in mesh relation and the remainder in star arms each radiating from a mesh angle in a plurality of different ways so that E. M. F. polygons having a number of sides greater than that of supply but less than the number of sections applied to the ends ot said star arms produce for all connections the same number of bands oi current equally spaced in phase rela-tion, but for each connection a diiilierent phase disphufeinent between neighbouring sections, und means i'or dist i rting` the l). M. F. polygon olf sup ply to the :i'orms required ior said diliercnt connections.

27. ln combination a polyphase source of supply, u dynamo electric machine, a primary winding on said machine divided into sections, means ifor connecting said sections .in a plurality of groups such that a polgV- phase supply applied to a group produces c'urreiits of larger phase number in the sections oit the group, means for connecting seid groups to the supply so as to produce e, given number or poles, and means for reversing the order of the phases applied to one group and for shifting the phase of the currents in all the s ctions of each other group through a given angle the same 'for all the sections ot a `group and reversing the order of the phases to produce another pole number.

28. In con'ibination a polyphase source ot supply, a dynamo electric machine, a pri mary winding` on said machine divided into sections, means connecting` a sub-multiple of 'the whole number oii sections into a grou p, means ior connecting said group and the remainingv sections to the source of snppliT to produce a given pole number, and means for varying the connections o' said group as a Vwhole und ot the remaining sections with the supplyto produce another pole number.

29, A method oif connecting; :i windiim`r` divided into sections which is required to produce tu'o pele numbers such that the phase diiierence between neig'nbouring,` sections on one pole niunber is the supplement of the phase difference between neig-h iiouring; sections on the other pole number, which consists in joining alternate sections o f the winding lor both pole numbers into a syn'imetrical networi; and joining the remaining sections into one network for the one pole number and into a dili'erent netuforlr 'For Athe other pole number,

3d A method of conne-cting, :i winding divided into sections which is required to produce two pole nun'ibers such that the sum ci the two numbers oi pole pairs is equal to a siil3-imiltiple of the munher oit sections, which consists 'in joining; ttor both pole numbers a group ol equally spaced sectirms iformiiig such sub-multiple into a synnnetrical network, alternate sections oi a siii-cup being vjoined into a mesh und the rei'nuiniug sections oi a lgroup into star arms radiuti y `from the junctions oit said mesh, and join-- 'ng the remaining sections 'into other net- Works.

In testimony whereof l signi my nume to this specification.

FREDERICK CR-EEDY. 

